Mass bonding of twisted pair cables

ABSTRACT

A tape cable structure includes several sets of twisted wire pairs which are laminated so that the twist points are in a fixed phase relation with each other. In one embodiment, even twist length ratios between the adjacent twisted pairs are used. The relationship between the twist points can be adjusted to permit mass termination of the cable. When severed as by a heat knife along a transverse section of the tape at which the twists of all pairs are in phase, the two tape sections are drawn apart to expose substantially parallel bare wires ready for connection.

[ 51 May 29,1973

[54] MASS BONDING OF TWISTED PAIR CABLES [75] Inventor: Albert MalcolmWittenberg, Short Hills, NJ.

[73] Assignee: Bell Telephone Laboratories, Incorporated, Murray Hill,NJ.

22 Filed: Apr. 27, 1972 21 Appl. No.: 248,311

174/117 F, 117 AS, 117 FF, 74 R, 32, 33, 34;339/95 R, 17F

[5 6] References Cited UNITED STATES PATENTS Pearson .;...174/34 5/1951Wald ..174/34 X 2,550,891 3,239,916 3/1966 Love 3,459,878 8/1969Gressitt ,174/117 R ri ary E qmi err QQ d r A tt0rney- R. J. Guenther,Edwin B. Cane et a1.

[57] ABSTRACT A tape cable structure includes several sets of twistedwire pairs which are laminated so that the twist points are in a fixedphase relation with each other. In one embodiment, even twist lengthratios between the adjacent twisted pairs are used. The relationshipbetween the twist points can be adjusted to permit mass termination ofthe cable. When severed as by a heat knife along a transverse section ofthe tape at which the twists of all pairs are in phase, the two tapesections are drawn apart to expose substantially parallel bare wiresready for connection.

5 Claims, 3 Drawing Figures MASS BONDING OF TWISTED PAIR CABLES FIELD OFTHE INVENTION This invention relates to laminated tape cable and morespecifically to the mass terminating of such cables in which pairs ofwires are twisted.

BACKGROUND OF THE INVENTION Laminated tape cable is finding increasingusage in the wiring of medium and large scale electronic equipment suchas in the back plane of computer hardware, in electronic telephonecentral offices, and in electronic PBXs. A significant cost-saving isrealized by using laminated tape cable versus stringing individualconductors, because mass termination techniques may be employed with thetape cable.

Mass terminating, however, with its attendant cost advantages occursonly for tape cable in which the wires are essentially straight andparallel to one another. In this type structure, the positions of theconductors are fixed for the entire length of the cable. Yet, in manyinstances, it is desirable that the wire pairs of a tape cable betwisted. For this configuration, mass terminating techniques have notbeen available for want of a structure that is readily skinnable andalso that duplicates the advantages of conductor parallelism found inthe usual tape cable.

Accordingly, the following are objects of the invention:

to devise a structure of laminated twisted pair cable that is amenableto mass bonding;

to avoid having to individually strip, sort, and then bond wires of alaminated twisted pair cable; and

to realize the advantages both of twisted pairs and laminated tape cablein a single structure without accruing a cost penalty.

SUMMARY OF THE INVENTION The above and other objects are achievedpursuant to the-invention by a tape cable structure in which severalsets of twisted wire pairs are laminated in a thermoplastic material sothat the twist points are in a fixed phase relation with each other. Inone embodiment even twist length ratios between the adjacent twistedpairs, such as 2:4:8 are used. In general, twist lengths are selected sothat, from an initial in-phase position at a first cable cross section,there will occur at periodic intervals the same in-phase relationshipbetween the conductors.

Pursuant to one aspect of the invention, the plastic laminate sheet isprovided with edge notches at the 1 point where all pairs are in phase.For pairs having a 2:4:8 relationship, the notches may alternatebetween, for example, a square and a triangular geometry. Thisfacilitates identification of points where a wire in each pair, say thetip wire of a tip and scale pair, is in phase with every other tip wire;or where one tip wire is exactly out of phase with the others.

Pursuant to a primary aspect of the invention, stripping is accomplishedby first terminating the cable to its desired length and then severingthe plastic laminating material and the wire insulation so that thenecessary amount of bare wire will be eventually exposed to make theelectrical connections. The lamina and insulation are cut along a crosssection corresponding to a point where all twist-pair loops are at theirmaximum separation in the plane of the cable. This is readily achieved,for example, with a hot-knife stripper. Then, the two severed sectionsof lamina with the insulation still imbedded in each are separated bysliding the short end off the wire. The wires, although of differenttwist lengths, straighten out because of their initial parallelism atthe stripping point due to their in-phase relationship. The wires thencan be laid onto terminals or connector blocks and bonded in arelatively simple operation as done for laminated tape cable.

The invention and its further objects, features, and advantages will bemade more readily apparent by a reading of the following detaileddescription of illustrative embodiments and by reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic perspectivediagram of a laminated twisted pair cable embodying the invention;

FIG. 2 is a side schematic view showing the tape cable of FIG. 1 beingprepared by hot-knife techniques for bonding; and

FIG. 3 is a schematic perspective diagram showing placement of theprepared twisted pair cable upon an exemplary terminal block.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT As seen in FIG. 1,the laminated twisted pair cable of the present invention designatedgenerally as 10 consists of plastic insulated conductor pairs 11, 12,13, 14 which have respectively twist lengths that shall be denoted A, B,C, D respectively, where twist length D may equal twist length A assuggested in FIG. 1. The conductor insulation alternatively can belacquer. The gauge of the wires advantageously is 19 gauge or above. Thetape medium consists of lamination layers 15, 16 which are made ofpolyvinyl chloride, for example, or some equivalent thermoplasticmaterial whose properties are that it can maintain the position of thewires while the insulation is removed, and that it be readily strippedby some means, such as a hot knife.

The laminate method is conventional except that the pair twists may becontrolled during the laminating process by methods and apparatus suchas described, for example, in the US. Pat. No. 3,579,823 of T. J.Gressitt issued May 25, 1971, and assigned toapplicants assignee whichto the extentrelevant is hereby incorporated by reference.

An alternative structure for the tape medium is a single layer such aslayer 15, to which the conductors are suitably adhered or attached.

The structure of the present invention calls for laminating the wirepairs 11-14 with different twist lengths whose ratios with respect toone another are chosen so that at relatively closely spaced intervals anin-phase relationship between the wires will occur. More particularlythe in-phase relationship is at a point where, for each of the conductorpairs 11-14, there periodically exists the maximum separation betweenthe conductors of each given pair at the same point in the plane of thecable. These in-phase points occur in the structure shown in FIG. 1 atcross sections of the cable 10 that are designated 17, 18, 19respectively. Point 18 is where one cable is 180 out of phase with theother sirable to provide edge notches having alternating shapes. Thus,the square-shaped edge notches 20 designate a cross section at which thetip conductor of pair 13 is in the up position; and the triangular notch21 denotes a cross section at which the ring conductor of pair 13 is inthe up position. This arrangement aids an installer in identifying tipand ring wires, not only of pair 13 but also of the other pairs in thecable preparatory to mass bonding.

FIG. 2 illustrates a hot knife 22 with opposing jaws 23, 24 thatadvantageously are mounted as opposite sides of a conventional notedhand tool, not shown. The jaws-23, 24 are positioned with respect to oneof the two types of edge notches, heat is applied through the jaws, andthe underlying plastic lamina as well as the plastic insulation of theconductor pairs 11-14 are parted.

Then, pursuant to the invention, the cable portions to either side ofthe part line are drawn apart manually in opposite directions asindicated by arrow 25, creating a gap 26 between the two sides. In thisprocess, the wires of the conductor pairs 11-14 assume parallelism overthe gap 26 width, by virtue of their initial orientation at the criticalcross section.

The cable is now ready to be applied to a terminal block 27 shown inFIG. 3. It is obvious that the two sides of cable 10 can be separatedprior to this operation and the side which is to form no part of theconnection simply discarded. It is possible to make twisted pairsinsulated with a thin lacquer. The twists are usually very tight, butcan nevertheless be spread at certain points where stripping would takeplace. Alternatively there could be provided a periodic straightsection. it is seen that these cases are served also by the presentinvention.

In preferred inventive embodiments, the plastic laminating material mustbe sufficiently strong to resist the tendency of the conductors in eachpair to close-in on each other as the gap 26 is opened. Furthermore, theplastic laminating material advantageously must adhere strongly to thewire insulation, but the wire insulation, in turn, should have lessadhering strength with respect to'the wires. It has been found that goodresults pursuant to the teachings of the present invention are obtained,with polyvinyl chloride insulated wires and with thin polyvinyl chloridesheets. Other arrangements are of course readily envisionable within theinventive teaching.

Various specific twist length ratios will occur to practitioners skilledin the art. As a general rule, the twist length design should be guidedby the need to minimize electrical interaction (crosstalk) betweennearby wire pairs.

It is to be understood that the embodiments described herein are merelyillustrative of the principles of the invention. Various modificationsmay be made thereto by persons skilled in the art without departing fromthe spirit and scope of the invention.

What is claimed is:

1. A tape cable comprising:

a longitudinally continuous insulative compliant tape medium;

a plurality of plastic insulated conductor pairs attached alonggenerally parallel paths to said medium, each pair having apredetermined different twist length, the twist lengths being selectedto create at periodic transverse positions along said medium an in-phaserelationship among all said twisted pairs;

said medium being capable of being severed along any one of saidtransverse sections and the severed parts drawn apart with the tapemedium and said plastic conductor insulation mutually adhering, therebyto expose a zone of bare wires spaced apart, substantially parallel andready for connection.

2. A tape cable pursuant to claim 1 wherein said tape medium comprisesfirst and second sheets laminated together with said plurality of pairssandwiched thereinbetween.

3. A tape cable pursuant to claim 2 wherein said tape medium furthercomprises edge notches placed at the positions of said transversesections for identification phase relationship is represented by amaximum mutual separation between the conductors of each pair occurringconcurrently at said transverse positions.

1. A tape cable comprising: a longitudinally continuous insulativecompliant tape medium; a plurality of plastic insulated conductor pairsattached along generally parallel paths to said medium, each pair havinga predetermined different twist length, the twist lengths being selectedto create at periodic transverse positions along said medium an in-phaserelationship among all said twisted pairs; said medium being capable ofbeing severed along any one of said transverse sections and the severedparts drawn apart with the tape medium and said plastic conductorinsulation mutually adhering, thereby to expose a zone of bare wiresspaced apart, substantially parallel and ready for connection.
 2. A tapecable pursuant to claim 1 wherein said tape medium comprises first andsecond sheets laminated together with said plurality of pairs sandwichedthereinbetween.
 3. A tape cable pursuant to claim 2 wherein said tapemedium further comprises edge notches placed at the positions of saidtransverse sections for identification thereof.
 4. The apparatus ofclaim 1 in combination with a connector element comprising a row ofspaced upright metallic pins, the spaced-apart conductors of each saidpair straddlIng a respective said pin.
 5. A tape cable pursuant to claim1, wherein said in-phase relationship is represented by a maximum mutualseparation between the conductors of each pair occurring concurrently atsaid transverse positions.